Date Arithmetic in PHP

Question

Is there a PHP function I can use to do something like the following:

• Get the date 6 months ago (e.g. now - 6 months)?
• Get the date 2 years from now (e.g. now + 2 years)?

Answer 1

Yes, there is: strtotime():

1. 6 months ago: strtotime("-6 months");
2. 2 years: strtotime("+2 years");

These will return Unix timestamps. So you might want to put the result into date() or localtime() or gmtime().

Please do not try to subtract 6 months or add 2 years of seconds to time(). This does not take into account things like daylight saving or leap seconds and still gives you a value in seconds which is unlikely to be the precision you need. Let the library functions do it.